Electrical oscillation generator



June 21, 1932. MCL bN 1,864,368-

ELECTRICAL OSCILLATION GENERATOR Filed April 2. 1927 3 Sheets-Sheet l INVENTOR ALEXANDER McLEAN NICULSON ORNEY ELECTRICAL OSCILLATION GENERATOR Filed April 2. 1927 3 Sheets-Sheet 2 IIHHIHII g INVENTOR ALEXANDER McLEAN Mcopson ORNEY June 21, 1932. McL. NICOLSON ELECTRICAL OSCILLATION GENERATOR Filed April 2. 1927 2' Sheets-Sheet 3 INVENTOR. ALEXANDER McLEAN NICOLSON 6) ATTORNEY Patented June 21, 1932 UNITED STATES PATENT @FFHQE ALEXANDER MCLEAN NICOLSON, OF NEW YORK, N. Y., ASSIGNOB, BY MESNE ASSIGN- MENTS, T0 WIRED RADIO, INQ, OF NEW YORK, N. Y., A CORPORATION WARE OF DELA- ELECTRICAL OSCILLATION GENERATOR Application filed April 2, 1927.

This invention relates to apparatus for producing electrical oscillations, and more particularly to such apparatus utilizing thermionic vacuum tube amplifiers in connection with piezo-electric crystal devices adapted to stabilize and control the frequency of the oscillations generated.

It is an object of this invention to provide a method and apparatus for generating electrical oscillations, the frequency of which is maintained absolutely constant.

It is a further object of this invention to provide apparatus of the class described having a substantially non-reactive coupling between the output circuit of the amplifier and the input circuit thereof.

It is a further object of this invention to provide apparatus utilizing a substantially non-reactive coupling between the output circuit and the input circuit of the amplifier, either or both of which circuits may comprise tuned circuits for the purpose of approximately determining the frequency of the oscillations to be generated by the system.

The features of novelty which I believe to be characteristic ofmy invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and as to its practical embodiments will best be understood by reference to the specification and accompanying drawings, in which: 7

Fig. 1 illustrates diagrammatically apparatus in accordance with one form of my invention.

Fig. 2 illustrates apparatus according to a difierent form thereof.

Fig. 3 illustrates apparatus of a still further modified form of my invention, and

Fig. 4 illustrates a still further modification and for some purposes the preferred form of my invention.

In accordance with my invention, I provide an amplifier system preferably in the form of one or more thermionic vacuum tubes each having a cathode adapted to emit electrons, a control electrode and an anode. For the purpose of producing sustained oscillations, I interlink the output and input circuits of the Serial No. 180,421.

amplifier system so as to transfer energy from the output circuit to the input circuit.

According to my invention, a portion of the input and output circuits may be electrically or mechanically interlinked in such manner as to cause sustained oscillations. In each instance, I may utilize a tuned circuit for ap proximately determining the frequency at which the system Will oscillate: and likewise, in each instance, I may utilize a piezo-electric crystal device for exactly determining this frequency.

In accordance with one form of my invention, the piezo-electric crystal device is connected in the output circuit of the amplifier. Under other conditions, I may provide a plurality of piezo-electric crystal devices, one connected in the output circuit and another connected in the input circuit of the amplifier, and with means for transferring energy therebet-ween.

Referring now more particularly to Fig. 1, 1 designates a thermionic vacuum tube amplifier having a cathode 2 preferably in the form of a filament adapted to be heated by suitable source such as battery 3 to electronemitting temperature. The vacuum tube amplifier may also comprise a grid or control electrode 4 and an anode 5. The output circuit of the amplifier 1 comprises a piezoelectric crystal device 6 having a pair of electrodes 7 and 8, a suitable coil 9 and a suitable source of energy such as battery 10. The input circuit comprises coil 11, variable if desired, variable condenser 12, and a portion of the coil 9 so chosen as to feed back energyin the proper sense to generate sustained oscillations. A suitable coil 13 may be coupled with coil 9 for the purpose of supplying the oscillations generated by the system to the desired load.

The piezo-electric crystal device 6 may be a section of quartz, cut and ground to the desired dimensions, to produce the desired frequency, or it may comprise a crystal of Rochelle salt exhibiting the Well known hour glass configuration, or any other suitable piezo-electric device.

Such devices may vibrate at a number of resonant frequencies depending upon the particular mode of vibration: and for the purpose of selecting between the resonant frequencies of the device, I provide a means for tuning the input circuit, in the form of coil 11 and variable condenser 12.

In operation of the system, the frequency generated will be controlled by tuning the input circuit to one or another of the natural frequencies of the piezoelectric crystal device 6. The output current all passes through the crystal 6, part by reason of the resistance of the crystal, and part by reason of its piezoelectric activity and since the crystal resistance is relatively high, the output circuit is substantially aperiodic except at natural resonant frequencies of the crystal.

Referring now more particularly to Fig. 2, in this instance the input circuit of the thermionic amplifier 1 comprises piezo-electric crystal device 21 having electrodes 22 and 23. The input circuit is connected between the control electrode 4 and cathode 2. The output circuit comprises suitable battery 10 and a suitable coil 16, and in shunt wit-h coil 16, there is provided a variable capacity 17 forming a tuned circuit. Piezo-electric crystal device 18 having electrodes 19 and 20 is also included in the output circuit, shunted if desired by choke to permit the flow of direct current. The piezo-electric crystal device 18 is mechanically coupled in any suitable manner by mechanical coupling, diagrammatically shown as 24, to the piezo-electric crystal device 21.

In the operation of the system shown, the energy impressed upon the piezo-electric crystal device 18 is controlled by adjustment of the capacity 17 or of the coil 16, or both: and it will be seen that a series circuit is formed by coil .16 and condenser 17 in parallel, and electrodes 19 and 20 of the crystal device 18. The impression of oscillatory energy upon the crystal device 18 causes it to vibrate, which vibrations are communicated to the crystal device 21, resulting in the generation of electro-motive forces which appear on electrodes 22- and 23. By control of the tuning circuit comprising inductance 16 and capacity 17, the natural frequency of vibration of the crystal devices may be selected and the frequency of oscillation determined, from which it will be seen that a number of different frequencies may be generated as desired by the same apparatus, by readjustment of the tuning circuits.

Referring now more particularly to Fig. 3, I have shown a form of my invention, in which the amplifier system 1 comprises a series of resistance coupled amplifier tubes: in this instance, the amplifier tube 1 comprises in its output circuit a resistance and battery 10. An additional amplifier 33 having a cathode 34, an anode 35, and control electrode 36 has its input circuit connected across resistance 30 through capacity 31. The output circuit of the amplifier 33 comprises suitable resistance 39. The resistance 39 is connected in the input circuit of a suitable amplifier 40 having cathode 41, anode 42, and control electrode 43. Suitable blocking condenser 38 is interposed in the input circuit thereof. Suitable resistance 32, and biasing battery 37 are connected between grid 36 and cathode 34, and suitable resistance 48 and biasing battery 44 are connected between grid 43 and cathode 41. The inductance 16 shunted by suitable resistance 45 is connected in the output circuit of amplifier 40 and connected to the electrodes 19 and 20 of piezo-electric crystal device 18 through variable capacity 46. I

It will be noted that in this instance coil 16, condenser 46, and crystal 18 form a series tuned oscillating circuit, the impedance of which may be controlled by variation of its constants. Tht energy impressed on the crystal 18 may be selectively controlled as to frequency by this circuit, and thereby the natural frequency of oscillation of crystal 18 is controlled. Under certain conditions, I find it desirable to utilize a resistance connected between the grid and filament of amplifier 1.

Likewise, as will be understood, the variation of the input circuit tuning by means of condenser 25 in conjunction with coil 26, if utilized, will serve to select the frequency at which the system will oscillate.

It will be understood that additional stages may be utilized in connection with the apparatus shown in Figs. 1 and 2, just as in Fig. 3.

It will be understood that the piezo-electric crystal devices vibrate mechanically and electrically at one or another of their resonant frequencies. The tuning circuits operate to select one or another of the natural frequencies of Vibration of the crystal device or devices, from which it will be understood that an approximate tuning is all that is necessary. Inother words, a variation of the capacity 25 in such a manner as to change the reactance of the condenser 25 and the inductance 26 from inductive to capacitive by passing through the resonance point, while it may change the phase of the currents flowing, will not change the frequency of the currents which will take place only when the circuits are so adjusted as to cause the crystal devices to vibrate at a different resonant frequency. It will be understood that inductance 26 and condenser 25 may be ar ranged in a series with each other and with crystal 21 instead of in parallel as shown.

Referring now more particularly to Fig. 4, I have shown a still further modification of my invention. In this instance, the output and input circuits of the amplifier are interlinked through suitable piezo-electric crystal device .50, having-a common filament r ground electrode 53, and input electrode 2 connected to grid 4 of tube 1, and an elecrods 51 connected to a tap 54 which may be adjusted on coil 16. Also, condenser 55 is provided interposed between coil 16 and resistance 45.

Also, a common filament battery 56 is provided, with switch 57 in series therewith, and individual rheostats 58, 59 and 60 for controlling the filament circuits. This, however, is per se, no part of my invention.

It will be noted that in this instance, the adjustment of the tap 54 and the selection of the capacity of condenser 55 varies the constants of the output circuit, and the natural frequency thereof, while the impression of oscillations between electrodes 51 and 53 causes the production of oscillations between electrodes 53 and 52 corresponding to one or another of the natural frequencies of the piezo-electric crystal 50.

lVhile I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the spirit and scope of my invention, as will be understood by those skilled in the art.

I claim:

1. In an oscillation generator, a space discharge tube amplifying element, and a frequency controlling element, said frequency controlling element comprising a palr of piezo-eleotric devices mechanically connected together and non-reactive means for coupling one of said devices with the input circuit of said amplifying element and the other of said devices with the output circuit of said amplifying element to cause the generation of constant frequency oscillations.

2. In an oscillation generator, a space discharge tube amplifying element having input and output circuits, and a frequency controlling element, said frequency controlling element comprising a piezo-electric device, a resonant circuit, means for coupling the input circuit of said amplifying element with said resonant circuit and with said piezo-electrio device, and means connecting said piezoelectric device with the output circuit of said amplifying element including a second piezoelectric device mechanically connected to the first mentioned piezo-electric device.

3. An amplifying system comprising a thermionic relay having an anode, a cathode and a control electrode, and a path for transferring energy from the output side of said relay to the input side thereof, said path comprising an output circuit and an input circuit associated with said relay, at least one of said circuits being tuned, and a plurality of piezoelectric crystal devices mechanically connected one to another, said path being so arranged as to constitute a non-reactive coupling and forming the sole channel for transferring energy from the output of said relay to the input thereof through said plurality of piezo-electric crystal devices.

4. An amplifying system comprising a thermionic relay having an anode, a cathode and a control electrode, and a path for transferring energy from the output side of said relay to the input side thereof, said path comprising an output circuit and an input circuit associated with said relay, at least one of said circuits being tuned, and a plurality of piezoelectric crystal devices, said path being so arranged as to constitute a non-reactive coupling and forming the sole channel for transferring energy from the output of said relay to the input thereof, one of said piezo-electric crystal devices being disposed in said input circuit and the other of said piezo electric crystal devices being connected in said output circuit for the generation of oscillations in said circuits.

Signed at New York, in the county of New York and State of New York, this 30th day of March, A. D. 1927.

ALEXANDER MCLEAN NICOLSON. 

